The present invention relates to an LED driver system incorporating an added open/short detection system, and more particularly to LED matrix open/short detection apparatus and method for detecting and indicating a faulty LED connection in LED display panel 200. LED display panel can be used as backlight or displaying character or indicating lights in many applications. If there is a fault in LED connection, the function of LED display panel will be affected and it cannot fulfill the purpose of applications.
There are two types of LED connections in most of the applications arranged in matrix form: normal conventional connection and cross-plex connection as shown in FIGS. 1B and 1A. In both connections, there are control algorithm circuit 300, LED driver system 100 which consists of power MOS 105 to 108 for conventional and 106 to 109 for cross-plex, PWM controlled current sources 101 to 104 for conventional and 101 to 105 for cross-plex connection, and LED panel 200 which consists of LEDs 201 to 216. As shown in FIG. 1B, for normal conventional connection, power MOS 105 controlled by Y1 and PWM controlled current source 104 controlled by X1, must be turned on to light up LED A1 201, where A1 is the coordinates of the particular LED in the matrix. But for the cross-plex connection shown in FIG. 1A, power MOS 106 controlled by Y1 and PWM controlled current source 104 controlled by X2 must be turned on in order to light up LED A1 201. In cross-plex connection, turning on the corresponding Y and X together at the same time (e.g. Y1 and X1, Y2 and X2 and so on) is prohibited.
Conventional means to detect open/short connection in the LED panel 200 would be to use current injection technique, as described in US2003/0160703 (Fault Diagnosis Circuit For LED Indicating Light) by Takahiro Kurose and Sakai-shi.
This technique, however, cannot be used for cross-plex LED connection and cannot detect individual LED faulty connection. This is because, the technique used in US2003/0160703 is designed for individual LEDs arranged in the conventional connection, and hence will not work properly for cross-plex connection. It also uses many components in the system. It is the objective of the present invention to overcome the abovementioned problems associated with the prior art, and is able to be utilized for detecting open/short conditions for individual LED in both conventional and cross-plex connections.